CN102066997A - Method for manufacturing an optical waveguide, optical waveguide, and sensor arrangement - Google Patents

Abstract

A method for manufacturing an optical waveguide is proposed, in which a waveguide structure comprising a waveguide layer of ZnS- SiO2 (220) is deposited on a first layer (210), wherein a first refractive index of the first layer is lower than the refractive index of the waveguide layer. A sensor arrangement comprising a planar optical waveguide, a light source, a sensor, an application unit for applying an analyte on top of the planar waveguide and a processor connected to the sensor is provided as well.

Description

Method for manufacturing an optical waveguide, optical waveguide and sensor device

technical field

Embodiments of the invention relate to methods for fabricating optical waveguides. Other embodiments of the invention relate to optical waveguides and sensor devices, respectively.

Background technique

Waveguides are spatially inhomogeneous structures used to guide light (ie, to limit the spatial region in which light can propagate). It can be used, for example, to transmit light over long distances (e.g. in communication systems), guide light on integrated optical chips (silicon photonics), maintain high light intensity over relatively long distances (e.g. in waveguide lasers and frequency doublers) , exfoliation of the highest-order transverse modes, interaction of light guided in an evanescent field with a material (eg, in some waveguide sensors), or splitting and combining beams. Typically, waveguides contain regions of increased refractive index compared to the surrounding medium. However, it is also possible to guide by using reflections, for example at metal interfaces.

There are many different techniques for fabricating waveguides. Some examples include lithography using semiconductor, crystal, and glass materials combined with e.g. ion exchange or thermal fusion, drawing from a preformed drawn fiber to further reduce the size of the waveguide to make an optical fiber, creating nanowires, using focused A pulsed laser beam writes waveguides in transparent media, utilizing laser-induced breakdown, epitaxy, and polishing methods used to fabricate planar waveguides. Switching between different manufacturing technologies can be complicated. This may involve issues such as cost of fabrication, adaptability and reproducibility, achieved propagation loss, possible negative effects (e.g. by heating or undiffused material), optimal mode size and symmetry for coupling to other waveguides aspect.

A planar waveguide is a waveguide with a planar geometry. It is usually fabricated in the form of a thin transparent film or layer of increased refractive index on some substrate or possibly embedded between two substrate layers.

Contents of the invention

Therefore, there remains a need for additional material systems that provide reliable methods to produce optical waveguides with low absorption losses.

This object is solved by a method, an optical waveguide structure and a sensor arrangement according to claims 1, 12 and 18, respectively.

Other embodiments are defined in the dependent claims.

Further details of the invention will become apparent with reference to the drawings and certain descriptions.

Description of drawings

Fig. 1 shows the main steps of an embodiment of the present invention;

Figure 2 shows a cross-sectional view of an optical waveguide according to another embodiment of the present invention;

Figure 3 shows a cross-sectional view of an optical waveguide according to another embodiment of the present invention;

Figure 4 shows a cross-sectional view of another embodiment of an optical waveguide;

Fig. 5 schematically shows a sensor device according to another embodiment of the present invention;

Figure 6 shows a cross-sectional view of another embodiment of an optical waveguide;

Figure 7 shows a cross-sectional view of another embodiment of an optical waveguide;

Figure 8a shows a graph depicting the wavelength dependence of the refractive index of an embodiment of a ZnS- _SiO waveguide; and

Figure 8b shows a graph depicting the wavelength dependence of the absorption coefficient for an embodiment of a ZnS- _SiO2 waveguide.

Detailed ways

In the following detailed description, reference is made to the accompanying drawings which form a part hereof, showing by way of illustration specific embodiments in which the invention can be practiced. To this end, directional terms such as "top", "bottom", "front", "rear", "front", "rear", etc. are used according to the orientation of the figures being described. Because components of embodiments of the present invention may be oriented in a number of different orientations, directional terminology is used for purposes of illustration and not limitation. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. Therefore, the following detailed description is not to be considered in a limiting sense, and the scope of the invention is defined by the appended claims.

Hereinafter, embodiments of the present invention are described. It is worth noting that all described embodiments below can be combined in any way, ie there is no limitation that these described embodiments cannot be combined with each other.

In FIG. 1, in step S100, a first layer having a first refractive index is provided.

In step S102, a waveguide structure is deposited on the first layer, the waveguide structure includes a waveguide layer composed of zinc sulfide (ZnS)-silicon oxide (SiO ₂ ), the refractive index of the first layer is lower than that of the waveguide layer. The material zinc sulfide-silicon oxide ZnS-SiO ₂ may also be referred to as (ZnS) _{100 -x} -(SiO ₂ ), where x represents the weight percent of silicon oxide.

Using the method described above, an optical waveguide 200 shown in cross-section in FIG. 2 is obtained. The waveguide structure 205 includes a waveguide layer 220 . In the illustrated embodiment, there are no other layers in the waveguide structure 205 . However, as explained with reference to another embodiment below, the waveguide structure 205 may comprise other layers. In the case where the first layer 210 has a lower refractive index than the waveguide layer 220, light coupled into the waveguide layer 220 will remain in the waveguide layer 220 if the waveguide layer 220 has a low absorption coefficient and can Loss cases are guided.

As shown in Fig. 8b, the ZnS- _SiO2 material system used for the waveguide layer exhibits a low absorption coefficient for wavelengths in the visible region and near infrared region.

ZnS- _SiO2 is a mixture of two components, namely, zinc sulfide and amorphous silicon oxide as small grains. The refractive index of this material system depends on the amount of ZnS or _SiO2 respectively. If more _SiO2 is present, the refractive index is lower. In the visible region, the refractive index of pure ZnS is about 2.3, which decreases approximately linearly to 1.85 for the material system of 50% ZnS and 50% _SiO2 .

The first layer 210 may be a substrate, for example providing a two-layer system. The substrate can be made of glass or polymer, both of which have a lower refractive index than that of ZnS—SiO ₂ . The substrate can be realized by one material, but the substrate can also comprise a plurality of different layers, wherein the uppermost layer (ie the layer in contact with the waveguide structure 205) has a refractive index smaller than that of the waveguide layer.

The first layer may also be a silicon-based material, for example, silicon oxynitride (SiON), SiCON, or SiCO ₂ .

In FIG. 3 , an optical waveguide 300 is shown formed by depositing a first layer 210 on another substrate 310 before depositing a waveguide layer 220 or waveguide structure 205 on top of the first layer 210 . In this embodiment, the first layer 210 serves as an intermediate layer between the waveguide layer 220 or waveguide structure 205 and the further substrate 310 . Some materials that may be used as the other substrate 310 (eg, some polymers such as polycarbonate (PC)) may have large absorption coefficients for the wavelengths used. For an additional intermediate layer 210 disposed between the further substrate 310 and the waveguide layer 220 or the waveguide structure 205, the absorption losses within the waveguide layer 220 or the waveguide structure 205 can be adjusted by appropriate selection of the thickness t of the first layer 210. The first layer should have a low absorption coefficient for the used wavelength of light within the waveguide layer 220 or waveguide structure 205 . A material that can be used for the first layer 210 is _SiO2 , which has a low absorption coefficient and is easy to deposit on substrates made of glass, silicon or polymers.

Substrate 310 may be made of semiconductor material or glass or polymer (plastic).

Because, for example, the refractive index of ZnS- _SiO can be greater than 2.0 for an _amount of SiO below about 30%, the first refractive index of the first layer 210 can be selected between 1.3 and 2, or between 1.4 and 1.8, Or between 1.4 and 1.6. In each case, the condition that the refractive index of the first layer 210 is smaller than that of the ZnS—SiO ₂ waveguide layer is met.

A waveguide layer or waveguide structure may be deposited on top of the first layer 210 by a low cost and fast physical vapor deposition process such as a sputtering process. For sputtering, deposition rates greater than 2 nm/s can be achieved, which is greater than that of other similar waveguide materials (eg _Ta2O5 and _{TiO2 )} . The attenuation of the ZnS- _SiO2 based waveguide _structure or waveguide layer is comparable to that of _Ta2O5 and _TiO2 layers deposited by evaporation process.

In the sputtering process, targets composed of ZnS or ZnS- _SiO2 can be used. Using a commercial sputtering system with a typical power of 4.5 kW and a ZnS sample, a thickness uniformity of ±2.5% for the waveguide layer can be achieved at a substrate diameter of 120 mm and a deposition rate of about 13 nm/s. Better uniformity values can be obtained if smaller substrates are used. A refractive index uniformity of ±0.11% can be achieved using a sputtering process.

It is also possible to deposit waveguide layers or waveguide structures by very costly ion plating processes or by chemical vapor deposition processes or plasma enhanced chemical vapor deposition processes.

The content of ZnS in the waveguide layer 220 may be between 10% and 95%, or between 50% and 90%, or between 70% and 90%. Material systems with a zinc sulfide content of less than 100% are not brittle and are therefore easy to handle.

In FIG. 4 , another embodiment of an optical waveguide 400 is shown comprising a cladding layer 410 of a second material having a second refractive index on top of the waveguide layer 220 or waveguide structure 205 , wherein the second refractive index smaller than the refractive index of the waveguide layer 220 . The cladding layer 410 ensures that the waveguide layer 220 or the waveguide structure 205 is deposited between two layers (ie, the first layer 210 and the second layer 410 ) both having a refractive index smaller than that of the waveguide layer. Additionally, the cladding 410 may serve to prevent physical damage to the waveguide layer 220 or waveguide structure 205, eg, by stretching or impact. For example, the coating can also be used to protect against chemical effects such as corrosion, or as an adhesion promoter for another layer, or to reduce surface roughness. Overlay 410 may consist of one or more sublayers. The thickness of the cladding layer 410 is not limited.

Optical waveguides 200, 300 and 400 are shown in Figures 2, 3 and 4 as planar waveguide structures that guide light in one direction, ie in the direction in which layers are stacked on top of each other. Light can only travel in waveguide layers or waveguide structures.

However, it is also possible to use waveguide structures composed of ZnS- _SiO2 , which are further configured, for example, as ridge waveguides, which can also guide light in other directions, for example approximately perpendicular to the direction in which light is guided in planar waveguides.

In FIG. 5 a sensor device 500 is shown comprising an optical waveguide 300 comprising a substrate 310, a first layer 210 and a waveguide layer 220 or waveguide structure 205, wherein the first layer 210 has a lower refractive index than the waveguide layer 220 refractive index. The waveguide layer 220 is made of ZnS- _SiO2 having a refractive index greater than 2.0. The sensor arrangement further comprises a light source 510, a sensor 540 and/or another sensor 540A and/or 540B, and a processor 550 connected to the sensor 540 or to the plurality of sensors 540, 540A, 540B. Analyte 530 is applied on top of waveguide layer 220 or waveguide structure 205 .

Light 555 from light source 510 is coupled into waveguide layer 220 or waveguide structure 205 by diffraction grating 560 and guided through waveguide layer 220 or waveguide structure 205 . In the region where the analyte 530 is in contact with the surface of the waveguide layer 220 or waveguide structure 205 , a portion of the light 555 acts as a so-called evanescent field in the analyte 530 .

A second diffraction grating 570 may be provided to couple out light 555 and detect the outcoupled light with sensor 540 to generate an auxiliary signal that is forwarded to processor 550 . The auxiliary signal depends on the properties of the analyte (eg its concentration) and thus can be used to determine said property. Optionally, light coupled out from the analyte may be received directly by additional sensors 540A, 540B.

Other embodiments for coupling light 550 into waveguide layer 220 or waveguide structure 205 may include prisms or side coupling schemes for coupling light.

In the context of this description, the term analyte is to be understood as the substance to be analyzed itself or a system comprising the substance to be analyzed. Detection is achieved in one or more steps of analysis during which the surface of the waveguide layer 220 or waveguide structure 205 is exposed to one or more solutions. A solution used may include detectable. The analyte can also be free of fluorescent components if the fluorescent substance is absorbed on the waveguide region. Analytes may also include components such as pH buffers, salts, acids, bases, surfactants, viscosity action additives or dyes.

The analyte may be a biological medium, eg egg yolk, a body fluid or a component thereof, especially blood, serum, plasma or urine. Analytes may also be surface waters, solutions or extracts from natural or synthetic media (eg, soil or plant parts), solutions from biological processes, or synthetic solutions. Analytes can be used without dilution or addition of solvents.

Light can be detected at different positions, for example, light emitted from fluorescent substances or scattered light can be directly detected, or light emitted from the waveguide layer or waveguide structure at the edge of the waveguide layer or waveguide structure can be detected, etc.

As the fluorescent compound, a functional fluorescent dye (for example, a dye including rhodamine, a fluorescein derivative, etc.) having fluorescence in a wavelength range of 330 nm to 1000 nm can be used.

It is advantageous to use different fluorescent dyes that can all be excited by light of the same wavelength but have different emission wavelengths.

It may be that the analyte contacts the waveguide structure 205 while at rest or passes continuously through the waveguide structure, both of which enable flow-through to be turned on or off.

Transient excited light or scattered light or loss of light intensity can be detected by photodiodes, photocells, photomultipliers, CCD cameras and detector arrays such as CCD standard CCD arrays. Light can be projected through optical elements such as mirrors, prisms, lenses, Fresnel lenses, and graded index lenses to the aforementioned photodiodes, photocells, photomultipliers, CCD cameras, and detector arrays such as CCD licensed CCD arrays , to detect light.

In Fig. 6, another embodiment of an optical waveguide 600 is shown. As mentioned above, waveguide structure 205 may include one or more layers in addition to waveguide layer 220 . In this embodiment, an intermediate layer 610 is formed between the waveguide layer 220 and the first layer 210 . The intermediate layer 610 may enhance the adhesion of the waveguide structure 205 to the first layer 210, or may improve surface properties such as roughness. Intermediate layer 610 may consist of one or more sublayers.

In Fig. 7, another embodiment of an optical waveguide 700 is shown. In this embodiment, the waveguide structure 205 includes a further layer 710 on top of the waveguide layer 220 . Another layer 710 may be used, for example, to adapt to surface properties such as surface tension, surface roughness, improve abrasion resistance, or to protect waveguide layer 220 from chemicals used as analyte 530 in the sensor device of FIG. 5 . Another layer 710 may be a light transmissive material having a low absorption coefficient in the wavelength region used. For example, a thin layer of Ta ₂ O ₅ (tantalum pentoxide) having a refractive index of about 2.1 may be used as the further layer 710 . The optical properties of this waveguide structure 205 are comparable to those of a single ZnS—SiO ₂ -based waveguide layer 220, but with improved chemical resistance. Other possible _material systems for the further layer 710 may include, but are not limited to, _TiO2 (titanium dioxide), _Si3N4 (silicon nitride), or _SiO2 (silicon dioxide). Another layer 710 may consist of one or more sub-layers.

The thickness of the further layer 710 depends on the desired function, but in most cases the thickness should be as small as possible so as not to interfere with the function of the waveguide. For example, to improve the chemical resistance of the ZnS—SiO ₂ -based waveguide layer 220, a 10 nm layer of Ta ₂ O ₅ as another layer 710 is sufficient, depending on the chemical reaction used. Therefore, the thickness of the further layer 710 can be selected from between 1 and 100 nm, preferably between 2 and 20 nm.

Materials used for the other layer 710 may also be used for the middle layer 610 . In addition to the waveguide layer 220 , the waveguide structure can also include an intermediate layer 610 and a further layer 710 .

In Fig. 8a, the measured relationship of the dependence of the wavelength of the output light on the refractive index is shown. These values were measured on samples with a waveguide layer thickness of 60 nm and a ZnS to _SiO2 ratio of 80:20 (wt%). The diagram shows a decrease in the refractive index from n=2.4 at a wavelength of 350 nm to n=2 at a wavelength of 950 nm.

In Fig. 8b, the measured relationship of the dependence of the wavelength of the output light on the absorption coefficient k is shown. These values were measured on samples with a waveguide layer thickness of 60 nm and a ZnS to _SiO2 ratio of 80:20 (wt%). The graph shows that the absorption coefficient decreases from 10 ⁻¹ at a wavelength of 350 nm to 10 ⁻⁵ at a wavelength of 950 nm.

Inventive optical waveguides and methods for manufacturing optical waveguides are provided, which result in low absorption loss optical waveguides with high deposition rates, thus effectively reducing the manufacturing cost of said optical waveguides.

Claims (18)

1. method that is used to make optical waveguide, it comprises the steps:

Ground floor with first refractive index is provided; With

Deposit waveguiding structure on described ground floor, wherein, described waveguiding structure comprises ZnS-SiO ₂Ducting layer, and described first refractive index is less than the refractive index of described ducting layer.

2. method according to claim 1, wherein, in the step process of the described waveguiding structure of deposition, before the described ducting layer of deposition on the described middle layer, deposition first middle layer on described ground floor.

3. method according to claim 1 and 2, wherein, described ground floor is the substrate of being made by glass, polymkeric substance or semiconductor material.

4. method according to claim 1 and 2 also comprises the steps:

Before the step of the described waveguiding structure of deposition, the described ground floor of deposition on substrate.

5. method according to claim 4, wherein, described substrate is made by glass, polymkeric substance or semiconductor material.

6. according to the described method of arbitrary claim in the claim 1 to 5, wherein, described ground floor is by SiO ₂Make.

7. according to the described method of arbitrary claim in the claim 1 to 6, wherein, by a kind of technology from the set of forming by physical gas-phase deposition, ion plating process, evaporation technology, chemical vapor deposition method, plasma reinforced chemical vapour deposition technology and sputtering technology, carry out the step of the described waveguiding structure of deposition.

8. according to the described method of arbitrary claim in the claim 1 to 6, wherein, carry out the step that deposits described waveguiding structure, wherein in described sputter procedure, use ZnS target or ZnS-SiO by sputtering technology ₂Target.

9. according to the described method of arbitrary claim in the claim 1 to 8, wherein, the content of ZnS is between 70% to 90% in the described ducting layer.

10. according to the described method of arbitrary claim in the claim 1 to 9, wherein, in the step process of the described waveguiding structure of deposition, on described ducting layer, deposit another layer.

11., also comprise the steps: according to the described method of arbitrary claim in the claim 1 to 10

Deposition has the coating of second material of second refractive index on the top of described waveguiding structure, and wherein said second refractive index is less than the refractive index of described ducting layer.

12. an optical waveguide, it comprises:

Ground floor, it has first refractive index; With

Waveguiding structure, it is positioned on the top of described ground floor, and wherein said waveguiding structure comprises ducting layer, and described ducting layer comprises ZnS-SiO ₂, described ducting layer has the refractive index greater than described first refractive index.

13. optical waveguide according to claim 12 also comprises:

Substrate, wherein said ground floor are sandwiched between described substrate and the described waveguiding structure, and described substrate is made by glass, polymkeric substance or semiconductor material.

14. according to claim 12 or 13 described optical waveguides, wherein, described ground floor is by glass, SiO ₂, semiconductor material or polymkeric substance make.

15., also comprise according to the described optical waveguide of arbitrary claim in the claim 12 to 14:

Coating, it has second refractive index, and wherein said waveguiding structure is sandwiched between described coating and the described ground floor, and described second refractive index is less than the refractive index of described ducting layer.

16. according to the described optical waveguide of arbitrary claim in the claim 12 to 15, wherein, described waveguiding structure comprises the middle layer that is formed between described ducting layer and the described ground floor.

17. according to the described optical waveguide of arbitrary claim in the claim 12 to 16, wherein, described waveguiding structure comprises another layer on the top that is formed at described ducting layer.

18. a sensor device, it comprises:

Planar optical waveguide, it comprises:

Ground floor, its have first refractive index and

Planar waveguiding structure, it is positioned on the top of described ground floor, and wherein said waveguiding structure comprises ducting layer, and described ducting layer comprises ZnS-SiO ₂, and described ducting layer has the refractive index greater than described first refractive index;

Light source, it is configured to provide the light that is coupled in the described planar optical waveguide;

Sensor, it is configured to detect auxiliary signal according to described light; With

Processor, it is connected to described sensor, and described processor is configured to determine according to described auxiliary signal the parameter of analyte, and described analyte is applied on the top of described Planar Optical Waveguide Structures.

Images